On Mon, Dec 17, 2012 at 11:45 PM, Nikita Popov <nikita....@gmail.com> wrote:
> On Mon, Dec 17, 2012 at 11:03 PM, Stas Malyshev <smalys...@sugarcrm.com>wrote: > >> Hi! >> >> > Basically the method allows you to do delegate error handling to the >> > coroutine, rather than doing it yourself (as you are not always able to >> do >> > it). It is particularly useful in more complicated settings, e.g. if you >> > are doing task scheduling through coroutines. For a small sample of how >> >> Could you expand on this point a bit more? It sounds like using >> exceptions for flow control, which is usually a very bad idea. >> >> > this looks like see http://taskjs.org/. What the ->throw() method >> would do >> > in these examples is that it allows to check for errors by try/catching >> the >> > yield statement (rather than going for some odd solution with error >> > callbacks). >> >> Could you point to some specific example? >> > The basic idea behind this kind of task management is that you can do > asynchronous operations just like you would synchronous ones, i.e. without > the need for callbacks or wait-loops. Whenever the functions wants to > perform some async action it doesn't directly do it, rather it yields the > operation that does it. The scheduler then waits until that operation is > finished (running other tasks in the meantime) and only resumes the > coroutine once it is finished. This way you can write async code without > the ugliness that is usually involved with async code. > > Here is an example to get a rough idea of how the use looks like: > > function server() { > // ... > $stuff = yield $socket->recv(); > // ... > yield $socket->send($response); > // ... > } > > The throw() method comes in when you want to handle errors on those > asynchronous operations. Without it you would be forced to use error codes. > throw() allows you to do the error handling just like you would normally > do. E.g. consider that $socket->send() were a fallible operation. Then you > could catch errors like this: > > function server() { > // ... > try { > yield $socket->send($response); > } catch (SocketException $e) { > // do some error handling > } > // ... > } > > In this case the outside code (where the exception comes from) can't know > what it should do in case of an error. Only the code in the coroutine knows > that. That's why you need some possibility to throw the error into the > context that knows how to deal with it. > > I hope that this makes it a bit more clear. > > Nikita > If there are no further objections I'll commit this tomorrow. Nikita
